Blue Mage is a masterpiece of game design.

[Reynhart]

It's fun to me, accelerating strategies, plotting builds, and obtaining an edge.

I can understand that. But if you take your PLD70 to OS mobs and exploit the job changing system, you're not really "optimizing BLU", you're simply not playing it.

It would be basically the same as searching how to obtain an HQ 100% on a really difficult item...by simply buying it on the market board.

I wouldnt be surprised if they decided to create only limited jobs after they notice "you have (soon) 17 jobs to pick, we are done with them, here take a limited job instead".

Considering balance is more and more difficult the more job you add, I wouldn't be surprised by that. And I wouldn't personally mind as long as each limited job bring a new mechanic to the game.